.trans{
  transition: transform .2s ease;
}
@size: 40px;
.sider-trigger-a{
  padding: 7px 14px;
  width: 100%;
  height: 40px;
  display: inline-block;
  text-align: center;
  color: #5c6b77;
  margin-top: 0;
  border-bottom: 1px solid #35404e;
  i{
    // .trans; // 收起动画效果
    display: inline-block;
    vertical-align: top;
    width: 100%;
    background: #404c5a;
    border-radius: 4px;
    color: #fff;
  }
  &.collapsed {
    padding: 7px;
    i{
      transform: rotate(180deg);
      display: inline-block;
      // .trans; // 收起动画效果
    }
  }
}
